/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      https://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.jexl3.internal;
  
  import java.util.List;
  import java.util.Map;
  import java.util.Objects;
  import java.util.Set;
  
  import org.apache.commons.jexl3.JexlContext;
  import org.apache.commons.jexl3.JexlEngine;
  import org.apache.commons.jexl3.JexlExpression;
  import org.apache.commons.jexl3.JexlFeatures;
  import org.apache.commons.jexl3.JexlInfo;
  import org.apache.commons.jexl3.JexlOptions;
  import org.apache.commons.jexl3.JexlScript;
  import org.apache.commons.jexl3.parser.ASTJexlScript;
  
  /**
   * <p>A JexlScript implementation.</p>
   *
   * @since 1.1
   */
  public class Script implements JexlScript, JexlExpression {
  
      /**
       * Implements the Future and Callable interfaces to help delegation.
       */
      public class Callable implements java.util.concurrent.Callable<Object> {
  
          /** The actual interpreter. */
          protected final Interpreter interpreter;
  
          /** Use interpreter as marker for not having run. */
          protected volatile Object result;
  
          /**
           * The base constructor.
           *
           * @param intrprtr the interpreter to use
           */
          protected Callable(final Interpreter intrprtr) {
              this.interpreter = intrprtr;
              this.result = intrprtr;
          }
  
          @Override
          public Object call() throws Exception {
              synchronized(this) {
                  if (result == interpreter) {
                      checkCacheVersion();
                      result = interpret();
                  }
                  return result;
              }
          }
  
          /**
           * Soft cancel the execution.
           *
           * @return true if cancel was successful, false otherwise
           */
          public boolean cancel() {
              return interpreter.cancel();
          }
  
          /**
           * Run the interpreter.
           *
           * @return the evaluation result
           */
          protected Object interpret() {
              return interpreter.interpret(script);
          }
  
          /**
           * @return true if interruption will throw a JexlException.Cancel, false otherwise
           */
          public boolean isCancellable() {
              return interpreter.isCancellable();
          }
  
          /**
           * @return true if evaluation was canceled, false otherwise
           */
         public boolean isCancelled() {
             return interpreter.isCancelled();
         }
     }
 
     /**
      * The engine for this expression.
      */
     protected final Engine jexl;
 
     /**
      * Original expression stripped from leading and trailing spaces.
      */
     protected final String source;
 
     /**
      * The resulting AST we can interpret.
      */
     protected final ASTJexlScript script;
 
     /**
      * The engine version (as class loader change count) that last evaluated this script.
      */
     protected int version;
 
     /**
      * Do not let this be generally instantiated with a 'new'.
      *
      * @param engine the interpreter to evaluate the expression
      * @param expr   the expression source.
      * @param ref    the parsed expression.
      */
     protected Script(final Engine engine, final String expr, final ASTJexlScript ref) {
         jexl = engine;
         source = expr;
         script = ref;
         version = jexl.getUberspect().getVersion();
     }
 
     /**
      * Creates a Callable from this script.
      * <p>This allows submitting it to an executor pool and provides support for asynchronous calls.</p>
      * <p>The interpreter will handle interruption/cancellation gracefully if needed.</p>
      *
      * @param context the context
      * @return the callable
      */
     @Override
     public Callable callable(final JexlContext context) {
         return callable(context, (Object[]) null);
     }
 
     /**
      * Creates a Callable from this script.
      * <p>This allows submitting it to an executor pool and provides support for asynchronous calls.</p>
      * <p>The interpreter will handle interruption/cancellation gracefully if needed.</p>
      *
      * @param context the context
      * @param args    the script arguments
      * @return the callable
      */
     @Override
     public Callable callable(final JexlContext context, final Object... args) {
         return new Callable(createInterpreter(context, script.createFrame(args)));
     }
 
     /**
      * Checks that this script cached methods (wrt introspection) matches the engine version.
      * <p>
      * If the engine class loader has changed since we last evaluated this script, the script local cache
      * is invalidated to drop references to obsolete methods. It is not strictly necessary since the tryExecute
      * will fail because the class won't match but it seems cleaner nevertheless.
      * </p>
      */
     protected void checkCacheVersion() {
         final int uberVersion = jexl.getUberspect().getVersion();
         if (version != uberVersion) {
             // version 0 of the uberSpect is an illusion due to order of construction; no need to clear cache
             if (version > 0) {
                 script.clearCache();
             }
             version = uberVersion;
         }
     }
 
     /**
      * Creates this script frame for evaluation.
      *
      * @param args the arguments to bind to parameters
      * @return the frame (may be null)
      */
     protected Frame createFrame(final Object[] args) {
         return script.createFrame(args);
     }
 
     /**
      * Creates this script interpreter.
      *
      * @param context the context
      * @param frame the calling frame
      * @return  the interpreter
      */
     protected Interpreter createInterpreter(final JexlContext context, final Frame frame) {
         return createInterpreter(context, frame, null);
     }
 
     /**
      * Creates this script interpreter.
      *
      * @param context the context
      * @param frame the calling frame
      * @param options the interpreter options
      * @return  the interpreter
      */
     protected Interpreter createInterpreter(final JexlContext context, final Frame frame, final JexlOptions options) {
         return jexl.createInterpreter(context, frame, options != null ? options : jexl.evalOptions(script, context));
     }
 
     @Override
     public JexlScript curry(final Object... args) {
         final String[] parms = script.getParameters();
         if (parms == null || parms.length == 0) {
             return this;
         }
         return new Closure(this, args);
     }
 
     @Override
     public boolean equals(final Object obj) {
         if (obj == null) {
             return false;
         }
         if (getClass() != obj.getClass()) {
             return false;
         }
         final Script other = (Script) obj;
         if (this.jexl != other.jexl) {
             return false;
         }
         if (!Objects.equals(this.source, other.source)) {
             return false;
         }
         return true;
     }
 
     @Override
     public Object evaluate(final JexlContext context) {
         return execute(context);
     }
 
     @Override
     public Object execute(final JexlContext context) {
         checkCacheVersion();
         final Frame frame = createFrame(null);
         final Interpreter interpreter = createInterpreter(context, frame);
         return interpreter.interpret(script);
     }
 
     @Override
     public Object execute(final JexlContext context, final Object... args) {
         checkCacheVersion();
         final Frame frame = createFrame(args != null && args.length > 0 ? args : null);
         final Interpreter interpreter = createInterpreter(context, frame);
         return interpreter.interpret(script);
     }
 
     /**
      * Gets this script captured variable, i.e. symbols captured from outer scopes.
      *
      * @return the captured variable names
      */
     public String[] getCapturedVariables() {
         return script.getCapturedVariables();
     }
 
     /**
      * @return the engine that created this script
      */
     public JexlEngine getEngine() {
         return jexl;
     }
 
     /**
      * @return the script features
      */
     public JexlFeatures getFeatures() {
         return script.getFeatures();
     }
 
     /**
      * @return the info
      */
     public JexlInfo getInfo() {
         return script.jexlInfo();
     }
 
     @Override
     public String[] getLocalVariables() {
         return script.getLocalVariables();
     }
 
     @Override
     public String[] getParameters() {
         return script.getParameters();
     }
 
     @Override
     public String getParsedText() {
         return getParsedText(2);
     }
 
     @Override
     public String getParsedText(final int indent) {
         final Debugger debug = new Debugger();
         debug.outputPragmas(true).indentation(indent).debug(script, false);
         return debug.toString();
     }
 
     /**
      * Gets this script pragmas
      * <p>Pragma keys are ant-ish variables, their values are scalar literals.
      *
      * @return the pragmas
      */
     @Override
     public Map<String, Object> getPragmas() {
         return script.getPragmas();
     }
 
     /**
      * @return the script AST
      */
     protected ASTJexlScript getScript() {
         return script;
     }
 
     @Override
     public String getSourceText() {
         return source;
     }
 
     @Override
     public String[] getUnboundParameters() {
         return getParameters();
     }
 
     /**
      * Gets this script variables.
      * <p>Note that since variables can be in an ant-ish form (ie foo.bar.quux), each variable is returned as
      * a list of strings where each entry is a fragment of the variable ({"foo", "bar", "quux"} in the example.</p>
      *
      * @return the variables or null
      */
     @Override
     public Set<List<String>> getVariables() {
         return jexl.getVariables(script);
     }
 
     @Override
     public int hashCode() {
         // CSOFF: Magic number
         int hash = 17;
         hash = 31 * hash + (this.jexl != null ? this.jexl.hashCode() : 0);
         hash = 31 * hash + (this.source != null ? this.source.hashCode() : 0);
         return hash;
         // CSON: Magic number
     }
 
     @Override
     public String toString() {
         CharSequence src = source;
         if (src == null) {
             final Debugger debug = new Debugger();
             debug.debug(script, false);
             src = debug.toString();
         }
         return src.toString();
     }
 }